Pulse Electrochemical Machining Research Articles

Precise pulse electrochemical machining by bipolar current: Aspects of effective technological application

This paper describes a method of pulse electrochemical machining (ECM) by bipolar current. The phenomenology of the main aspects of its efficient technological application is considered: • Ensuring long-time stability of geometric and physical-and-chemical properties of the working surface of the electrode-tool (ET) through the removal of cathode sedimentations. • Creating workpiece surface layers of special physical-and-chemical properties (change of the chemical composition, corrosion resistance, etc.) due to the creation of the chrome-concentrated layer on the surface of the chrome steel workpiece. • Reducing the height and changing the shape of microroughness on the machined surface, giving it mirror like brightness. • Increasing machining precision due to greater non-equipotentiality of the machined surface. • Improving ecological cleanliness of the ECM technology due to the reduced content of toxic ions of the six-valent chrome in the electrolyte when manufacturing workpieces of chrome steels.

Precise pulse electrochemical machining by bipolar currentAspects of effective technological application

Abstract This paper describes a method of pulse electrochemical machining (ECM) by bipolar current. The phenomenology of the main aspects of its efficient technological application is considered: • Ensuring long-time stability of geometric and physical-and-chemical properties of the working surface of the electrode-tool (ET) through the removal of cathode sedimentations. • Creating workpiece surface layers of special physical-and-chemical properties (change of the chemical composition, corrosion resistance, etc.) due to the creation of the chrome-concentrated layer on the surface of the chrome steel workpiece. • Reducing the height and changing the shape of microroughness on the machined surface, giving it mirror like brightness. • Increasing machining precision due to greater non-equipotentiality of the machined surface. • Improving ecological cleanliness of the ECM technology due to the reduced content of toxic ions of the six-valent chrome in the electrolyte when manufacturing workpieces of chrome steels.

Single-step electrochemical machining of complex nanostructures with ultrashort voltage pulses

We show that complex patterns including three-dimensional structures, lines, curved features, and arrays can be machined in substrates in single-step processing without the need for rastering. High-aspect-ratio nanometer accurate features were machined in nickel using ultrashort voltage pulse electrochemical machining. Experiments were conducted with two different tool shapes. The first was a combination of rectangles, squares, and a half circle; the second was a 2×2 array. The effect of pulse duration and electrolyte concentration on feature resolution was studied. Structures with 90 nm widths were made by applying 2 ns voltage pulses.

Development of electrochemical micro machining for air-lubricated hydrodynamic bearings

A specially-built EMM (Electrochemical Micro Machining)/PECM (Pulse Electrochemical Machining) cell, a electrode tool filled with non-conducting material, a electrolyte flow control system and a small & stable gap control unit are developed to achieve accurate dimensions of spindle recesses. Two electrolytes, aqueous sodium nitrate and aqueous sodium chloride are investigated in this study. The former electrolyte with few pits on the surface of workpiece has better machine-ability than the latter one with many pits on the surface of workpiece. It is easier to control the machining depth precisely with pulse electrical current than direct electrical current. This paper also presents an identification method for the machining depth by in-process analysis of applied electrical current and interelectrode gap size. The interelectrode gap characteristics, including pulse electrical current, effective volumetric electrochemical equivalent and electrolyte conductivity variations, are analyzed using the model and experimental results.

Identification of Interelectrode Gap Sizes in Pulse Electrochemical Machining

Pulse electrochemical machining offers significant improvements in dimensional accuracy as compared with conventional electrochemical machining. One primary issue in pulse electrochemical machining is to identify and control the interelectrode gap size. This paper presents an identification method for the gap size by in‐process analysis of machining current pulses. Stochastic modeling and analysis of the current pulses reveal two gap indicators: pulse signal variance and damping ratio. The variance has a linear relationship with the gap size within a commonly used gap range of 0.10 to 0.20 mm for a wide range of pulse durations. The damping ratio has been found to be highly correlated with the gap size. Laboratory experiments confirm the feasibility of this method under unevenly distributed gap conditions. The process mechanism underlying these findings is also discussed.

A combined electrical machining process for the production of a flexure hinge

A flexural hinge is required for various types of precision instruments and in precision location applications. The accuracy of the flexure hinge is a problem in mechanical machining processes and the ratio of satisfactory to defective end products is low. This paper proposes a combined electrical machining process of electrical discharge machining (EDM) and pulse electrochemical machining (PECM) for the production of a flexure hinge without deformation and residual stress. The application of the process has achieved notable results.

Modelling and Monitoring Interelectrode Gap in Pulse Electrochemical Machining

Pulse electrochemical machining (PECM) provides an economical and effective method for machining high strength, heat-resistant materials into complex shapes such as turbine blades of titanium alloys. The dimensional accuracy of PECM can be improved if a small interelectrode gap is maintained. This paper presents an interelectrode gap model for estimating machining parameters for the minimum gap size under the limit of electrolyte boiling. A specially-built PECM cell and a high speed data acquisition system are used to acquire the pulse current signal for developing an on-line monitoring strategy. A stochastic analysis of the current signal indicates a linear correlation between the gap size and the variance of the filtered current signal. An on-line monitoring system based on this correlation is proposed for the PECM process.

Modelling and Analysis of Pulse Electrochemical Machining (PECM)

A small interelectrode gap in Electrochemical Machining (ECM) results in improved dimensional accuracy control and simplified tool design. However, using a small gap with conventional ECM equipment adversely affects the electrolyte flow or mass transport conditions in the gap, leading to process instability. The most remarkable breakthrough in this regard is the development of ECM using pulsed current. Pulse Electrochemical Machining (PECM) involves the application of a voltage pulse at high current density in the anodic dissolution process. PECM allows for more precise monitoring and control of machining parameters than ECM using continuous current. Small interelectrode gap, low electrolyte flow rate, gap state recovery during the pulse-off times and improved anodic dissolution efficiency features encountered in PECM lead to improved workpiece precision and surface finish when compared with ECM using continuous current. This paper presents mathematical models for the PECM process which take into consideration the nonsteady physical phenomena in the gap between the electrodes, including the conjugate fields of electrolyte flow velocities, pressure, temperature, gas concentrations, current densities and anodic material removal rates. The principles underlying higher dimensional accuracy and simpler tool design attainable with optimum pulse parameters are also discussed. Experimental studies indicate the validity of the proposed PECM models.

Study of Pulse Electrochemical Machining Characteristics

The Pulse Electrochemical Machining (PECM) promises to improve dimensional accuracy control and to simplify tool design in machining hard, high strength, and heat resistant materials into complex shapes such as turbine blades. This paper presents a mathematical model for the PECM process which takes the non-steady physical phenomena in the gap into consideration. A specially-built PECM cell and a high-speed data acquisition device are used to obtain accurate experimental results in the gap for the model verification. The interelectrode gap characteristics, Including pulse current, metal removal rate, effective volumetric electrochemical equivalent and electrolyte conductivity variations, are analyzed based on the model and experiments.

The Investigation of the Flow Characteristics of the Gap in the Pulse Electrochemical Machining (PECM)

Summary This paper makes some systematic studies of the origination, the physical-mathematical characteristics and the disturbing function of the pressure wave in the inter-electrode gap, especially of the influence on the copying accuracy in PECM. Through the observation of high speed photograph to the real process in the gap and the analysis of precise measuring data for the pressure wave, we have recognized perceptually about the three respects. On the basis of the observation and analysis, a mathematical model of the gap pressure wave is deduced and verified, and by use of this model a simulated test by the digital computer is carried out. It is concluded that the gap pressure wave has a great influence on the copying accuracy in PECM.